Genetics and

Fruit Flies!

I. Fruit fly scientific name-Drosophila melanogaster

A. Drosophila-“dew lover” (dew-sugar)

B. Melanogaster -“black belly”

C. “Black bellied dew lover”

II. Diptera - 87,000 species of flies, gnats, & mosquitoes

A. Phylum -Arthropoda

B. Class - Insecta

C. Order - Diptera (two winged)

III. Adult fly body has 3 distinct regions

A. Head-sight & smell

B. Thorax attachment w/ 6 legs & 2 wings

C. Abdomen (largest)-digestion, reproduction, & respiration

IV. Can find them …A. Summer time

B. Swarming garbage pails

C. Swarming decaying

fruit

D. Mistaken for

gnats!

V. Characteristics

A. Taste receptor hairs-front legs1. Taste food by walking on it!!

B. “Sponging” mouth parts 1. Food must be in liquid form

2. Regurgitate digestive enzymes breaks down food-sponge it up!

C. Ocelli- scores of tiny, 6-sided facets in eyes

1. Can’t see sharp images but goodat detecting movement!

a.Humans see ~

1000 x’s better

D. 3 simple orange eyes of Drosophila

1. Boosters increase sensitivity of compound eyes to light

E. Antennae - 2 “feelers” head

1. Movable segmented organs-touch, smell, & taste

2. Locate decaying fruit by “smell”a. Alcohol produced

by fermentation

F. Hairs on body, legs, wings, & antenna1. Very sensitive to air & vibrations

G. Sex comb on male flies: dark hairs on front legs

1. Attract female attention before mating

H. Chitin - external skeleton 1. Muscles attached to skeletons on inside2. Do not fatigue easily3. Can fly continuously

=6 hours!4. Can fly ~ 2.5 mph!5. Wings beat

~ 250 times/second!

I. Haltere - club-shaped organ below ea. wing

1. Balancing instruments2. Wing moves up & haltere moves

down

3. If removed, “flies”

in circles!

VI. Food in vials mainly for larvae but adults eat it too!

A. Wheat, oat, soyflour, vitamins, salt,iron, sugar,preservatives, &yeast

B. Food coloring: easierto see larvae/ eggs

VII. Female fly can’t mateuntil ~ 10 - 12 hourspupa form

A. Pick females < 10 hrs old-virgins

B. Once mated female

retains sperm & lays fertile eggs

C. Drosophila egg

1. 0.2 mm long, shiny, white, translucent

2. Outer membrane pattern of hexagonal markings under a microscope

3. Eggs hatch

Breathing apparatus For larva

D. Small, white worm-like larva1. Three/four days eating food2. Stage lasts up to 5 days3. Shed outer covering (cuticle) twice 4. Instar - stage in btwn shedding

E. Larva-ready pupa crawls outof food

1. Outer layer darkens: hard-puparium

2. Worm-like larva changes into adult

a. 3-5 days-process metamorphosis: “change in form”

F. Young fly 1st emerges frompuparium

1. Almost white, abdomen very long

2. Head elongated,wings are wet & crumpled

3. Slowly forms adult features-few hours

4. Small flies do NOT grow into large flies

5. Size = size when emerge from puparium

6. Different sized flies= different species

G. Life cycle

1. Short, lasting 10-15 days, depends on temp

2. 30 generations of flies –studied in 1yr!

VIII. Drosophila -ideal animal forgenetics research

A. Easy to care for B. Small jars /vials containing special

food

C. Easy to tell males /femalesFEMALE MALE

D. Many offspring

E. During ~ 2 month lifetime = several hundred flies

IX. 100’s of genetic variationsin Drosophila

A. Affect body color, shape, pattern of body hairs, eye color & shape, & wing structure

B. Used in genetic studies since 1909

1. Thomas Hunt Morgan made genetic history a. Mated male fly w/white eyes withred eyed femaleb. New flies red eyes (showed

red eyes dominance)

c. F2 gen - 1/4 flies white-eye/malesd.1st genetic trait to be “sex-linked”

C. Discovery - 1 pair chromosomes determines sex 1. Fruit flies 8 chromosomes/body cell2. Morgan found males w/ bent

chromosome3. Called bent chromosome “Y” and the

other one, “X”

4. Therefore, males-XY & females-XX

Morgan’s Discovery

D. Other genetic manipulations

Normal Fruit Fly

X. Important commerciallyA. Gov. spent millions to keep pest under

control in CA & FL

B. Mediterranean fruit fly - Med Fly

C. Looks like house fly w/orange/black markings

D. If females are found - destroy crop to keep insect from establishing breeding population

XI. Our Experiment

A. Eye color is sex-linked in fruit flies

1. Red (wild type) dominant over

white (mutant)

B. Carolina Supply company provided P generation

1. White eyed females crossed with red eyed males

2. What is their genotype?

a. R = red eye r = white eye

b. XrXr ♀ XRY ♂3. What flies were

transferred to your vials (the F1 generation?)

Xr

Xr

XR Y

a.1 red eye female: 1 white eye male

XRXr XrY

XRXr XrY

C. Cross two F1 flies to predict your F2 generation

1. XRXr ♀ x XrY ♂

XR

Xr

Xr Y

XRXr XRY

XrXr XrY

2.Phenotypic ratio?

1 Red ♀ (25%) :1 Red ♂ (25%) :1 white ♀ (25%) :1 white ♂ (25%)

XII. Conclusions and vocabA. List 5 facts about fruit flies!B. List and define all vocab terms!